Pyrimethamine salt with 2-hydroxy-11h-benzo [a] carbazole-3-carboxylic acid



United States Patent M 1 (Jlaim. (Cl. 26i)--256.4)

The present application is a division of our copending application Serial No. 188,984, filed April 20, 1962, now US. Patent No. 3,161,641.

The present invention relates to a salt of 2,4-diamino- -(p-chlorophenyl)6-ethylpyrimidine with 2-hydroxy- 1lH-benzo[a]carbazole-3-carboxylic acid of the formula COOII and to methods for the production thereof.

The compound of the invention is produced by direct reaction of 2,4-diamino-5-(p-chlorophenyl) 6 ethylpyrimidine with 2-hydroxy-11H-benzo[a] carbazole-B-carboxylic acid, or by reacting a soluble salt of 2,4-diamino- S-(p-chlorophenyl)-6-ethylpyrimidine with a soluble salt of said acid. The term soluble salt is used herein in a relative sense and means a degree of solubility substantially greater than that exhibited by the product of the invention. Representative soluble salts of the pyrimidine base suitable for use in the process of the invention include the hydrochloride, hydrobrornide, hydriodide, sulfate, phosphate, sulfamate, acetate, lactate, tartrate, gluconate, citrate, and salicylate. Representative soluble salts of the acid that are suitable for use in the process of the invention include the alkali metal, alkaline earth metal, aluminum and amine salts. The invention comprehends the starting materials and final product in their hydrated as well as anhydrous forms. If desired, the starting materials used in the process can be converted in situ to the desired base, acid, or soluble salt form by treatment with an acid or base, as by neutralizing one or more of the carboxyl groups with base, by treatment of a carboxylatc salt with a mineral acid, by treatment of an acid-addition salt with a base, or by treatment of the pyrimidine base With an acid. The process of the invention is preferably carried out in a solvent in which the reactants are at least partially soluble and which is relatively unreactive toward each of the reactants. Suitable solvents include water, aqueous alkanols, dimethylacetamide, acetonitrile and mixtures thereof. Other satisfactory reaction media can be chosen from among a wide 3,244,716 Patented Apr. 5, 1966 variety of solvents, particularly those which are neutral and polar. The salt formation proceeds fairly rapidly upon mixing the reactants in the selected solvent. The process can be carried out at room temperature or below, although a high yield and a crystalline form con ducive to rapid filtration can be facilitated by heating the reaction mixture for up to about an hour and then chilling it. The reactants are customarily employed in equimolar ratio. When the reaction product precipitates directly it is isolated by filtration or centrifugation. In those instances when it does not precipitate directly it is first made insoluble by concentration of the reaction mixture or by dilution of the reaction mixture with a solvent in which the product is insoluble, and then collected.

The product of the invention is an antimalarial agent exhibiting especially long duration of action. It is known that 2,4-diamino-5-(p-chlorophenyl) 6 ethylpyrimidine, otherwise known as pyrimetharnine, is an antimalarial drug and is highly active against erythrocytic parasites. However, for collective prophylaxis the usual recommended adult dose is 25 mg. administered once a week. For large scale malaria eradication programs it is impractical to administer an antimalarial agent on such a frequent schedule. However, the compound of the present invention possesses the high antimalarial activity of 2,4- diamino-5-(p-chlorophenyl) 6 ethylpyrimidine, is nonirritating upon injection, and exhibits unusually long duration of action, thereby making it possible to extend the dosage interval from one week to as long as several months. The product of the invention can be formulated into suspensions which are pharmaceutically acceptable for intramuscular injection, using suspending vehicles such as 40% benzyl benzoate and castor oil, or water containing emulsifying or dispersing agents.

The invention is illustrated by the following example.

Example A solution of 1.39 g. of 2-hydroxy-l1H-benzo[a]carbazole-S-carboxylic acid in 25 ml. of hot dimethylacetamide is added to a warm solution of 1.24 g. of 2,4- diamino-5-(p-chlorophenyl)-6-etl1ylpyrimidine in ml. of methanol. Hot water ml.) is added and the salt is allowed to crystallize. The product is collected by filtration, dried and crystallized from an acetone-water mixture. The tan crystals thus obtained are the desired 2,4 diamino 5 (p-chlorophenyl) 6 ethylpyrimidine, salt with 1 formula weight of 2-hydroxy-11H-benzo[a]- carbazole-3-carboxylic acid, M.P. 289-295 C. (dec.).

We claim:

A salt of 2,4diamino-S-(p-chlorophenyl)-6-ethylpyrimidine with one formula weight of 2-hydroxy-11H-benzo- [a]carbazole-3-carboxylic acid.

References Cited by the Examiner UNITED STATES PATENTS 2,576,939 12/1951 Hitchings 260-2564 NICHOLAS S. RIZZO, Primary Examiner. 

